Damage evaluation of the steel tubular column subjected to explosion and post-explosion fire condition

摘要

Fires following explosion are considered one of the most serious secondary disasters in the blast events, which are frequently occurring in the terrorist attacks and other blast accidents. In the recent decades, a significant amount of research work has been carried out to study the structural response under blast loads, and it is found that due to the superior mechanical properties of steel material, steel structures are adequate to withstand a medium-scaled blast loading. However, since the strength of steel is sensitive to temperature, the post-explosion fire action should be involved in the evaluation of structural damage in the blast events. This paper is devoted to introduce a numerical method for predicting the integrative damage of steel tubular column subjected to blast load and the following fire action. The damage caused by blast load would significantly reduce the fire resistance of steel column, which includes two aspects: mechanical damage and geometrical damage. In order to describe the mechanical damage under the blast loading, a damage scalar is defined in the constitutive model, and it is used to represent the reduction of material strength. The geometrical deformation induced by blast load is treated as the initial condition in the fire analysis. Pressure-Impulse diagram is employed to describe the damage of the steel tubular column under blast loading. In the second step, fire analysis for the explosion-survived column is carried out. Obviously, the residual vertical capacity of steel column is related with the fire exposure time. In order to clarify the interaction between the explosion and the post-explosion fire action, a more inclusive function, characterized by three variables: pressure, impulse and fire exposure time, is presented in this paper, and it can be used to predict the residual capacity of the steel column subjected to blast load and exposed to fire for a specific time. In the last section, parametric studies are conducted to observe the effects of geometric size on the failure evolution of steel columns. The main objective of this research work is to provide guidance for assessing damage level of the steel tubular columns that have survived blast loading and expose to the following fire condition.